1. Field of the Invention
The invention relates to on-board central tire inflation systems (CTIS), for vehicles, by which the inflation pressure of the tires can be controlled from a remote location such as the cab. A CTIS enables the inflation pressure to be changed manually and/or automatically even when the vehicle is moving, utilizing an on-board source of compressed air or other fluid.
2. Description of the Prior Art
Central tire inflation systems are well known in the prior art, as shown by U.S. Pat. Nos. 2,634,782; 2,976,906; 2,989,999; 3,099,309; 3,102,573; 3,276,502; 3,276,503; 4,313,483; 4,418,737, 4,421,151, 4,434,833, and 4,724,879, which are incorporated herein by reference.
The traction of vehicles on soft terrain such as mud, sand or snow can be greatly improved by decreasing the inflation pressure of the tires; the contact area between the tires and the terrain (called the "footprint") enlarges. Decreasing the inflation pressure from that used on smooth highways also increases the riding comfort on rough roads. On the other hand, greater tire pressures, which are satisfactory for smooth roads, reduce the rolling resistance and tire carcass temperatures, increasing economy and safety.
A capability for changing the tire inflation pressure from within the cab of a cross country vehicle is especially useful for military trucks. They often travel in caravans in which stopping of one vehicle would delay others. If a tire were to be damaged by gunfire or the like, it might be partially inflatable so that the vehicle could continue. CTISs are very advantageous systems that are likely to be used much more in the future.
Prior art CTISs are not totally satisfactory, however, because their fluid valves, especially those near the tires, can be fouled by particles of rubber or dust that come up from inside the tires, especially during deflation operation.